There is known an electron beam irradiation device for irradiating an electron beam to a belt-shaped irradiated object and conducting a processing such as bridging, hardening or reforming to the irradiated object. As an irradiated object, for example, a resin film itself or a resin film coated with an electron beam curing resin coating is representative. However, in general, the reaction (processing) such as bridging of molecule induced by an electron beam is inhibited by oxygen existing in the atmosphere. For preventing the inhibition, for example, following methods are employed.
In an electron beam irradiation device described in the patent publication 1 an irradiated object is a film coated by an electron beam curing resin coating material. When the coating material coated on the film is bridged or cured by the electron beam, the coated film is brought into contact with a metal dram rotating at a circumferential speed synchronizing with the traveling speed of the film with a coating material being sandwiched therebetween, and in this state, the electron beam is irradiated from the film side. The electron beam irradiation device is of the type in which the electron beam curing resin coating material is blocked from oxygen existing in the atmosphere by making it contact the metal drum, and then the inhibition of curing (process for the irradiated object by electron beam) is prevented. Hereinafter such type is referred to as “type A”.
In the electron beam irradiation device of the type A, the electron beam is transmitted and penetrates all layers of the irradiated object and then reaches the layer (coating material) which need be processed by the electron beam. Therefore, a layer existing on the way of the beam, even though its do not need to be processed by the electron beam, is affected by the electron beam and undesirable reaction (such as yellowing or strength degradation) occurs. Part of the energy is absorbed in the layer on the way, thus the energy of the electron beam reaching the layer (coating material) which really need to be processed is wasted. The electron beam irradiation device needs a metal drum and a rotation drive mechanism thereof. Therefore, the device becomes heavy, thick, long and large more than required. Further, in a processing by the electron beam irradiation, especially in a curing process of coating material, a surface luster of the coating material is inevitably controlled by a surface luster of the metal drum.
As an electron beam irradiation device of the type which does not have such defects, following devices are known.
An electron beam irradiation device, described the patent application 2, the patent application 3, or the patent application 4 is of the type in which an electron beam is irradiated to an irradiated object in an irradiation chamber consisting of a shut space where an inert gas such as nitrogen is supplied, and is filled with the space. Hereinafter such type is referred to as “type B”.
Above irradiation chamber has a feed-in opening for feeding a belt-shaped irradiated object into the irradiation chamber and a feed-out opening for feeding the belt-shaped irradiated object out of the irradiation chamber. At the upstream (the upstream of the feeding direction of the irradiated object) of the feed-in opening in the irradiation chamber, a duct and a cavity for catching an X-ray of a bremsstrahlung are formed, and an air knife projecting as a nozzle toward the irradiated object for blowing an inert gas (nitrogen) in the cavity is provided. The air knife blocks oxygen in the air entering accompanied the irradiated object from the outside, and dilutes the oxygen which cannot be blocked.
That is to say, the type B prevents the inhibition of oxygen which may occur in the processing of the irradiated object by electron beam by dipping the irradiated object within an inert gas such as nitrogen which does not inhibit a process reaction by electron beam.
Patent Publication 1: JP-B-H05-36212
Patent Publication 2: JP-B-S63-8440
Patent Publication 3: JP-A-H05-60899
Patent Publication 4: J-U-H06-80200